Utility service providers employ numerous radio frequency (RF) utility meters, smart meters, sensors, and/or control devices (collectively “utility data collection devices”) as part of advanced metering infrastructures (AMIs) and/or automated meter reading (AMR) environments. These utility data collection devices are generally equipped with front-end modules (FEMs) that facilitate one- or two-way RF wireless communications.
To facilitate wireless communications, a utility data collection device has one or more antennas that interface to the FEM, such that each antenna is “impedance matched” to the FEM to minimize mismatch loss. Regarding transmission from a power amplifier, mismatch loss in transmission line theory is the amount of power generally expressed in decibels (dB) that will not be available on the output (e.g., a transmit antenna) due to impedance mismatches and signal reflections. A FEM that is properly terminated with the same impedance as that of the characteristic impedance of the antenna will have no reflections and therefore no mismatch loss.
In a factory setting, antennas are substantially impedance matched to their corresponding FEMs. However, after utility data collection devices are deployed in the field, numerous external influences can result is impedance mismatches between the FEM and the antenna of a utility data collection device. As an example, a utility data collection device may be located in a “non-friendly” RF enclosure, such as inside an all metal enclosure, covered with metal foil (e.g., intentional or unintentional tampering by a user), or the like. These externally induced impedance mismatches can give rise to reflections of a transmitted signal that may be strong enough to damage a power amplifier of an FEM, or cause a transmitted signal to become non-linear, degrading the signal-to-noise ratio (SNR) of a transmitted signal and increasing the difficulty of a receiver to receive the transmitted signal. Thus, these externally induced impedance mismatches can damage the FEM of a utility data collection device and/or degrade the signal transmitted by the utility data collection device.